Various types of seat belt and airbag systems have been used to protect passengers in automobiles, aircraft and other vehicles. In automobiles, airbags typically deploy from the steering column, dashboard, side panel, and/or other fixed locations. During a rapid deceleration event (e.g., a collision), a sensor detects the event and transmits a corresponding signal to an initiation device (e.g., a pyrotechnic device) on an airbag inflator. Initiation causes the inflator to release compressed gas into the airbag via a hose, thereby rapidly inflating the airbag.
Although airbags that deploy from stationary locations (e.g., a steering column) may be effective in automobiles, they may not be as effective in other types of vehicles having other seating arrangements. Seats in commercial passenger aircraft, for example, can be configured in a variety of layouts that provide different spacing between succeeding rows and adjacent seats. Moreover, such layouts may lack the availability of stationary structures upon which to mount airbags. Additionally, seatbacks in aircraft may rotate forward and downward during a crash or similar event, and thus may be unsuitable for airbag storage. As a result, airbags have been developed that deploy from seat belts to accommodate occupants in aircraft and other vehicles. Such airbags can deploy from, for example, a lap belt and/or a shoulder belt to provide additional protection during a crash or other rapid deceleration event.
Seat belt airbag systems include an electronic activation system positioned on or proximate to the seat to initiate airbag inflation. Electronic activation systems typically include a crash sensor (e.g., Hall effect sensors) that uses a magnetic field to detect rapid decelerations, which triggers a deployment circuit to activate the inflator and deploy the airbag. Some external magnetic fields, such as those found in loudspeakers, may be strong enough to activate the crash sensor and cause inadvertent airbag deployment. A magnetic shield, typically made from an expensive and heavy Mu-metal, is therefore positioned over the crash sensor to prevent such external magnetic fields from interfering with the operation of the crash sensor.